Solvability conditions and monotone iterative scheme for boundary-value problems related to nonlinear monotone potential operators

This article deals with boundary-value problems (BVPs) for the second-order nonlinear differential equations with monotone potential operators of type Au := ??(k(|?u|²)?u(x)) + q(u ²)u(x), x ∈ Ω ? R ⁿ . An analysis of nonlinear problems shows that the potential of the operator A as well as the potential of related BVP plays an important role not only for solvability of these problems and linearization of the nonlinear operator, but also for the strong convergence of solutions of corresponding linearized problems. A monotone iterative scheme for the considered BVP is proposed.     

Spectrophotometric determination of the soil fumigant: dazomet with copper(II)-neocuproine reagent

A spectrophotometric method has been developed for the assay of dazomet, a soil fumigant effective for the control of nematodes, germinating weeds and soil fungi, using the copper(II)-neocuproine (2,9-dimethyl-1,10-phenanthroline) oxidizing reagent. A highly colored copper(I)-neocuproine chelate formed immediately in ammonium acetate-buffered solution a result of the redox reaction with dazomet, and its concentration measured from the absorbance at 453 nm using a molar absorptivity of (3.35±0.15)×10⁴ l mol⁻¹ cm⁻¹ for dazomet, the LOD for soil being 1-2 ppm. Dazomet in commercial formulations (such as Basamit, BASF) and soil extract could be measured by the developed method which was rapid (color development took 5 min), and cost-effective. The developed method was as precise as the CIPAC HPLC method (at 95% confidence level) using a nucleosil 100-5 C₁₈ column with UV detection. The degradation of dazomet in different types of forestry soil, i.e. sandy, loamy and clay soils to which moisture and Basamit in recommended doses were applied, was followed kinetically using the developed procedure. The proposed method is much simpler than the US-EPA and CIPAC methods of dazomet assay, and is applicable to on-site colorimetry for field use (via retention of the colored copper(I)-neocuproine cation on an acidic cation exchanger) where rapid detection of dazomet residues and breakdown products is required. The method was not interfered with common soil ions and 1,3-dichloropropene (1,3-D), a fumigant used in combination with dazomet.     

Ab initio molecular dynamics simulation of pressure-induced phase transition in MgS

Pressure-induced phase transition in MgS is studied using a constant pressure ab initio molecular dynamics method, and a solid evidence of existence of its high-pressure phase is provided. As predicted by total energy calculations, MgS undergoes a structural phase transformation from the rocksalt structure to a CsCl-type structure under hydrostatic pressure. The transformation mechanism is characterized, and two intermediate phases having P4/nmm and P2₁/m symmetries for the rocksalt-to-CsCl-type phase transformation of MgS are proposed, which is different from the previously proposed mechanisms. We also study this phase transition using the total energy calculations. Our predicted transition parameters and bulk properties are in good agreement with the earlier first principle simulations.     

In silico evaluation of potential inhibitory activity of remdesivir,favipiravir, ribavirin and galidesivir active forms on SARS-CoV-2 RNA polymerase

Molecular Diversity - Since the outbreak emerged in November 2019, no effective drug has yet been found against SARS-CoV-2. Repositioning studies of existing drug molecules or candidates are...     

Simultaneous,Selective and Highly Sensitive Voltammetric Determination of Lead,Cadmium, and Zinc via Modified Pencil Graphite Electrodes

Pencil graphite electrode (PGE) modified with MWCNT and Bi³⁺ (MWCNT/Bi/PGE) was utilized in simultaneous analysis of Pb²⁺, Cd²⁺, and Zn²⁺. Surface and electrochemical characteristics of MWCNT/Bi/PGE were investigated via SEM, cyclic voltammetry, electrochemical impedance spectroscopy, and FTIR measurements. Even though modification with MWCNT did not improve the electroactive surface area, it significantly decreased the charge transfer resistance. Furthermore, modification with Bi³⁺ significantly increased the sensitivity. Finally, MWCNT/Bi/PGE exhibited the highest sensitivity and reproducibility compared to PGE and PGE modified with only MWCNT. MWCNT/Bi/PGE provided LOD values of 0.27, 0.43, and 1.63 μg L⁻¹, and linear ranges of 1–80, 5–80, and 10–80 μg L⁻¹ for Pb²⁺, Cd²⁺, and Zn²⁺, respectively. Proposed modification method offers effective electroanalytical performance with low time consumption and cost for the analyst.     

Two Electrons in a Quantum Dot: A Unified Approach

Low-lying energy levels of two interacting electrons confined in a two-dimensional parabolic quantum dot in the presence of an external magnetic field have been revised within the frame of a novel model. The present formalism, which gives closed algebraic solutions for the specific values of magnetic field and spatial confinement length, enables us to see explicitly individual effects of the electron correlation.     

Determination of Dimenhydrinate Nasal Delivery System in the Blood by RP-LC

Dimenhydrinate (DM) is used therapeutically for the prevention of motion sickness associated with nausea and vomiting. The aim of this investigation is the development of a new, rapid, sensitive, simple and fully validated RP-LC procedure for the suitable assay of DM in pharmaceutical formulation applied in blood samples. The method was validated before the amount determination studies in order to confirm linearity, precision, accuracy, selectivity, determination and quantification limit and consistency. High determination coefficient (r ²  = 0.998) of the standard curve drawn in the linearity studies showed that the line equation can be used in the quantification of the DM. Literature was reviewed for the methods based on diphenhydramine (DIP), its metabolite dimenhydrinate, in the in vivo determination of dimenhydrinate amount. The most appropriate method to be used in LC was decided to be the method applied by benefitting from the fluorescence characteristic of DIP. Maximum excitation and emission wavelengths in the developed method were scanned using multiple wavelengths and, maximum excitation and emission wavelengths were found to be 215 and 300 nm, respectively. In the validation study used to prove validity of the method, determination coefficient of the developed standard curve was calculated as 0.998 (RSD %), and line equation was concluded to be appropriate for use in amount determination studies. BBS % (1.06, 1.84 %) values obtained as “<2 %” in the intra-day and inter-day precision studies proved the precision of the method. Selectivity study revealed that other materials used in the formulation did not exhibit absorbance in the same wavelengths. Detection and quantification limit were found as 1 and 5 ng mL^?1, respectively. The determination of DM plasma concentrations using the proposed and fully validated LC assay has allowed us to characterize DMPK in the sheep, as well as determine DM relative bioavailability.     

X-Ray,Gamma, and Neutron Radiation Tests on Epoxy-Ferrochromium Slag Composites by Experiments and Monte Carlo Simulations

Radiation shielding effects of ferrochromium slag loading hardened epoxy resin samples were investigated. Five different samples including different percentages of epoxy resin and ferrochromium slag were produced. X-ray, gamma ray, and neutron particle transmission experiments were performed for epoxy-ferrochromium slag composites. Also, FLUKA Monte Carlo simulations were made to obtain absorbed doses. As a result, radiation shielding performance increases with increasing ferrochromium slag additive in epoxy.